Optimum machine clothing (i.e., forming wire, press fabric and dryer fabrics) run-ability depends on maintaining “like-new” permeability for an extended period of time. This can best be accomplished with an effective “deep cleaning”/conditioning program. During pressing, water that contains solids, fines, and other contaminants is removed from the bulk sheet and transferred to the machine clothing. Solids that accumulate in and on the machine clothing restrict removal of water from the bulk sheet. Over 10% accumulation is considered a heavily contaminated press fabric.
Cleaning/conditioning a forming wire typically utilizes a well directed shower in conjunction with caustic or caustic/aromatic hydrocarbon mix washing. The stubborn adherence of “macrostickies” (i.e., particles retained on a 0.15 mm slotted screen) on the forming wire surface leads to later problems such as wet end breaks, press section breaks, dryer section breaks, holes, sheet defects and high dirt counts. The end result of not removing macrostickies from the wire is unwanted downtime.
At present, the optimum press fabric cleaning/conditioning system utilizes both mechanical and chemical means to restore permeability. The mechanical means makes use of relatively high pressure showers and suction boxes. The shower water is usually, but not always, filtered to prevent particles larger than 100 microns from abrading the felt and the wash is usually carried out prior to contact with sheet side felt carrying rolls. Another sometimes neglected mechanical cleaning feature is the use of an oscillating needle water jet at controlled pressures. Proper oscillation of a high pressure cleaning shower is needed to assure uniform felt coverage—improper shower oscillation results in some areas of the felt remaining filled and some being cleaned (i.e., evident by streaky appearance).
At present, the optimum dryer fabric cleaning/conditioning system utilizes both mechanical and chemical means to restore permeability. The mechanical means makes use of relatively high pressure showers and scraping tools.
At present, the optimum surface and suction roll cleaning systems utilize both mechanical and chemical means to remove contaminates. These contaminants clog suction holes and interfere with the vacuum rolls ability to direct the bulk sheet in its turns through the machinery, causing breaks and downtime. Surfaces throughout the mill and the machinery become coated with these same contaminants, causing unsafe and unsightly conditions.
The chemical cleaners presently in use are either highly caustic (i.e., pH≧12) or caustic/aromatic hydrocarbon blends. Both are corrosive, and have physicals inappropriate for safe use (e.g., low flash points, components which are suspected carcinogens, etc.). The chemical systems are expected to remove hydrophobic contaminants such as adhesives, wax, wet strength resin, pitch and hydrocarbon oil, as well as inorganic precipitates such as clay, calcium carbonate, alum and titanium dioxide.
Efforts continue to provide efficient and environmentally sound chemical compositions that effectively clean substrates such as a paper machine clothing, surfaces, and suction rolls, as well as methods of removing microstickies and macrostickies from paper machine clothing, surfaces, and suction rolls.